1. Field of the Invention
This invention relates to a webbing lock mechanism used in a seatbelt system for locking an occupant restraining webbing as necessary, and particularly to a webbing lock mechanism designed to directly lock the intermediate portion of the webbing.
2. Description of the Prior Art
Heretofore, in general, there has been proposed such a construction of a webbing lock mechanism used in a seatbelt system that ratchet wheels are solidly secured to a take-up shaft for winding up the webbing from its end, and a pawl to be operated in an emergency of the vehicle is meshed with said ratchet wheels, whereby the webbing windoff rotations of the ratchet wheels and take-up shaft are locked. However, in the conventional webbing lock mechanism of the type described, even after the webbing windoff rotation of the take-up shaft is locked, the condition of loosely wound up webbing takes place until the respective layers of the webbing wound up onto the take-up shaft in layers come into tight contact with one another, thus causing a considerable length of webbing to be extended out.
To obviate the disadvantage as described above, there has been proposed a webbing lock mechanism capable of utilizing the tension of the webbing so as to directly lock the intermediate portion of the webbing when the tension of the webbing is increased in an emergency of the vehicle. In the webbing lock mechanism of the type described, a lock lever is pivotally supported by a frame, and the webbing is guided around the forward end of said lock lever, whereby the tension of the webbing in an emergency of the vehicle is imparted to the lock lever as an oscillating force, so that the oscillating force can be utilized to lock the intermediate portion of the webbing through lock members.
A roller is provided in said lock lever around which the webbing is guided so as to reduce the frictional resistance caused by the movement of the webbing. As the frictional resistance of the webbing at the roller is considerably high, the lock lever installed with a roller cannot satisfactorily reduce the resistance. Therefore, the occupant still feels high tension during windoff of the webbing from the take-up shaft.